1. Field Of The Invention
This invention relates to a nut fixing structure for a resinous case used for fixing a nut to the resinous case on the occasion of mounting, for example, the resinous gear case provided for a power window motor for a motor vehicle on the vehicle body using a bolt compatible with said nut.
2. Description Of The Prior Art
Heretofore, for example, in case of mounting a power window motor on the vehicle body, the motor is fixed to the vehicle body by tightening a bolt passed through a motor setting bracket provided on the vehicle body into a nut embedded into a resinous gear case provided for said motor by the insert molding process.
In this case, as shown in FIG. 7, protruding portions 53 having respective through holes 52 are formed at plural places on the outer periphery of a gear case 51, and a nut 52a is provided to the reverse side in FIG. 7 of the protruding portion 53 corresponding to a bolthole in the bracket by the insert molding process. The gear case 51 is fixed to the bracket by tightening the bolt into said nut 52a through the through hole 52.
However, when the gear case 51 is fixed to the motor setting bracket by tightening the bolt into the nut 52a insert-molded in the resinous gear case 51 at the time of mounting the power window motor on the vehicle body as described above, a gap may appear between the gear case 51 and the nut 52a due to difference of their thermal expansivity under the environment with outstanding temperature changes, and there is the possibility that play comes out between said power window motor and the motor setting bracket owing to looseness of the nut 52a. There is a problem since there is the possibility that the circumference of the nut 52a of the gear case 51 crumbles and the protruding portion 53 is cracked in case of applying tightening torque to the bolt too much.
Furthermore, there is another problem in that the manufacture of the resinous gear case 51 provided with the nut 52a by insert molding process can not necessarily contribute to the decrease of the cost.